Method of catalytic cracking of hydrocarbons utilizing a moving catalyst bed



May l, 1951 H. G. sHlMP METHOD oF CATALYTIC CRACKING oF HYDRocARBoNsUTILxzING A MOVING cATALYsT BED Flled Sept 27, 1947 caca/v6 ysa/0x7 6#wie Y i N E 0 n IN VEN TOR.

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Patented May l, 1951 METHOD F CATALYTIC CRACKING OF Y HYDROCARBONSUTILIZING A MOV- ING CATALYST BED Hans G. Shimp, Meylan, Pa., assignerto Houdry Process Corporation, Wilmington, Del., a corporation ofDelaware Application September 27, 1947, Serial No. 776,451

f The `and coke.

2 Claims.

, g l present invention relates to catalytic cracking in the vapor phaseof'oils heavier than gasoline, for example, gas oils and the like, tc

by yield and quality of liquid'product, to the 'temperatures ofadmission of the oil and catalyst streams to the reactor. Thus,overheating weil as producing relatively rapid coking of the heatingequipment. On the other hand, excessive catalyst inlet temperaturesresult in overcracking of vapor charge to non-liquid products, gas

2 It has been proposed toV achieve high yields of liquid including highoctane `gasoline by use of high feed rates of catalyst with respecttothe produce gasoline and otherrdesirable distillate charge. Sinceequipment for moving the cataproducts. In particular the invention dealswith 5 lyst and the actual movement Aof the same represueh cracking in ameving `catalyst system. In sont 'substantial items in the investmentand such systems the catalyst usually flows alternateoperating costs,respectively, of thef cracking 15r` and repeatedly thlQugh a reaction OrCracking plant,'use of high ratios of catalyst to oil results vessel anda regeneration vessel, in which latter in relatively high processingcosts. In addition, carbonaceous deposit accumulated on the catalysthigh ratios of catalyst to oil at otherwise equal during cracking isremoved by controlled burnconditions tend to increase conversion ofcharge ing. The invention is concerned with operation to non-liquidproducts. `Qi' the cracking Vessel hI'Ough Which, accord- When, in prioroperating methods, it has been Iing to preferred aspects and embodimentsof the P deemed advisable to use low. ratios of catalyst invention, thecatalyst oWs as a downwardly f and cil feed rates it has often beenfound necesmoving stream, in most instances as a compact or sary to soregulate the control conditions, inthe substantially continuous bed.interest of achieving either quality of gasoline In prior operation ofsystems of the character or yield of liquid product that the mostfavordescribed the catalyst entered the reactor at able balance of theseis not obtained;` temperature approximately or even somewhat 2,0 It hasbeen discovered in accordance with the A above desired maximum crackingtemperature. invention that substantially improved operation,Simultaneously, preheated and vaporized oil reflected in high quality ofgasoline and high yield charge Was admitted to the reactor adjacent itsof liquid product, is obtained in cracking systems .bottom to flow'countercurrently tothe descendof the typeA described when the movingcompact ing column of hot catalyst, the resulting rebody or bed ofcatalyst and preheated oil charge action products being withdrawn from'the reacvapors'are admitted to the reactor to flow downtion'vesseladjacent the top oi the moving bed wardly and co-ncurrentlytherethrough, resulting of catalysttherein. reaction products beingwithdrawn from the re- Three operating Yconditions controlled outsideactor afterl separation from the bed of catalyst of the reactordetermine largely the extent of :zo adjacent the lower portion of thebed. It is one cracking and yield of liquid products as well as of thefeatures of the invention that in its pracquality` of gasoline obtainedin reactors of given tice the rates of feed, oil vapors and catalyst tocatalyst content and charge capacity. These the reactor are` socontrolled that the heat conditions, hereinafter termed controlconditions, capacity of the oil is at least equal to and prefer are: (l)the temperature of the catalyst as ad- 35 ably greater than that of thecatalyst. Surprismitt'ed to the reactor; (2) the ratio of catalystingly,` at such ratios of catalyst to'oil, which and oil charges; and 3)the temperature to are relatively low, the advantages of high ratioswhich the oil charge is preheated. Increase in are rea1ized-without theexpense and other dis- ,any of these conditionsfresults in increasedtotal advantages. attendant upon their use. conversion or cracking ofthe charge to lower boil- 40 With typical` cracking catalysts presentlyin ,ing products, gasoline and gas. Also, with each commercial use, forexample, pellets or granules vof these conditions at relatively highlevel, pro- `of acid activated bentonitic clays or of synthetifductionof high anti-knock rating gasoline is cally prepared silica and aluminagel composites. ,favored` the maximum ratio of catalyst to oil contem-`v There are practical limits, however, determined plated by theinvention, equalityV of their heat capacities, lies within the range ofv3.5 .to 4.0, volumetric basis, for most vaporizable charge stocks Thisvolumetric relationship is expressed in terms of volume of a common sizeand shape of commercial pelleted catalyst mm. X 4 mm. cylinders)` pervolume of charge in. liguid or unvapo-rized condition. It is to beunderstood that equivalen-t volumetric ratios maybe usedwith ,catalystsro fl dierent physical form or lheat capacities tapparent density ofnormally packed 'f' pronounced.

catalyst particles multiplied by specific heat of the catalyticmaterial).

In practice of the invention, although relatively low catalyst to oilfeed rates are contemplated, the quantity of catalyst should be suicientthat a'substantial proportion ofthe sensible heat supplied to thecracking zone be sensible heat content of the catalyst. Thus, the heatcapacity of the catalyst feed should be at least one-third andpreferably at least half the heat capacity of the oil vapors.

For further description of the invention reference may be had to thesingle figure of drawing, which is a flow chart illustratingdiagrammatically one embodiment thereof.

As the drawing indicates, the cracking system comprises reactor l andregenerator or kiln 2, each being shown in schematic sectionalelevation. Cracking catalyst C, for example, in the Yform. Qf granulesor molded units, is moved contiriuous'ly and alternately through reactorI and fino.'- g, orereramy flowing downwardly through -each as asubstantially solid bed. Suitable conveyors', for example, mechanicalelevators 3 and ',4, transport the catalyst between kiln 2 and reactor lto maintain catalyst circulation at desired rate'.

l Regenerated catalyst at relatively high catalytic crackingtemperature, above 850 F. but preferably not in excess of about 1050 F.Vis adrnitted tothe top of reactor l as by line 5, and, preferably afterbeing uniformly distributed acrossthe reactorfis-flowed downwardlytherejthrough concurrently vwith hot vaporized oil charge which has beenpreheated in fired heater E and brought to theupper portion of reactor lA'by transfer line 'i' at cracking temperature of at least 820 E. butpreferablynot in excess of about 9252132, above which thermal crackingbecomes vI n reactor I the catalyst drops in temperature A over a rangeof cracking temperatures which in practice of the invention is usuallyof the order of 50 to 150 F. and resulting cracked products leave thereactor as by products line 8 after being "separated from the catalyst.

The latter, after being purged of absorbed hyfdrocarbons, for example,by steam admitted into elevator feed line S is transported to kiln 2 inwhichj carbonaceous or coky deposit resulting from the crackingreactions is removed from the `catalyst under controlled burningconditions which resultin increase of catalyst temperatureover the aboverange and delivery of the YAregenerated catalyst to reactor I and intocontactagain with hot charge vapors at the de `sired relatively highcracking temperature. As

shown, the regeneration may be effectedV by admission of air or othersuitable oxygen-bearing regenerating medium to kiln 2 and the catalysttherein at a plurality of spaced levels, the resulting flue gases beingwithdrawn at intermediate levels. As is often required by theconcenntration of deposit on the catalyst, the regenera- -'tion andfinal delivery temperature to the reactor may be controlled by use of asuitable num- ,ber of indirect heat exchange members disposed v in kiln2 through which a suitable heat exchange grjcooling medium iscirculated. g During regeneration and especially during thelatterportion `thereofY the catalyst temperature isljelevated o r is soregulated that, upon being dis- ,chargedflbm kiln Zuinto elevator 3 andconveyed 'thelatter and catalyst line 5 into the topof reactor i", itisat cracking temperature, preferfluids, air and hydrocarbons, present inkiln 2 and reactor l, respectively, the purging medium as admitted toeach is at pressure somewhat higher than that obtaining within thecatalyst at the nearest outlet for flue gas or hydrocarbon products.Also, to maintain reactor and kiln pressures at the desired level,usually low superatmospheric pressure, a suitable inert seal gas isadmitted to the kiln and reactor at a level above that at whichreactants, combustion supporting medium and hydrocarbon charge,respectively, arcadmitted to the catalyst. The seal gas, which may becarbon dioxide or fiue gas free or substantiallyA so of uncombinedoxygen, is supplied at pressure somewhat vabove desired reactionpressureto insure that the regenerating'medium and vhydroca'rbons arecontained within their respective reaction vessels. It is usuallydesirable to maintain a substantial pressure'differential be'- tweenelevator 3 and reactor l which it feeds, to which end a pressure legcomprising 'a vertical column of catalyst (not shown) may be interposedtherebetween. Suitable pressure differential between kiln 2 and elevator4 may be similarly obtained and maintained.

In practice ofthe invention the relative rates of iiow of hot catalystand preheated vaporizd charge are preferably established so that theheat capacity of the charge is somewhat greater than that of the hotcatalyst. Under these conditions, the ultimate control of crackingtemperatures (theintegrated average temperature of oil and catalystwithin the reactor) isl effected through the temperature ofthe enteringcharge, small change in the last named temperature resulting insubstantial adjustment of cracking severity corresponding approximatelyto the relative heat capacities of the two streams. Such temperaturechange of charge is easily effected by simple adjustment of fired heater6 without necessitating modification of the regenerating conditions. Infact, it is one of the features of the invention in its preferredaspects that ultimate control of cracking temperature be effected byregulation of oil feed temperature while feeding the hot regeneratedcatalyst to the reactor at constant or substantially constanttemperature, for example, within the range of 850 F. to 1050o F. butpreferably above about 900 F.

One of the important advantages of the invention is` that in itspractice high yields of high quality motor gasoline are obtained witheconomically low capacity of equipment for handling and moving thecatalyst. Moreover, surprisingly enough, when the concurrent flow andlimited reiative rates of feed of catalyst and oil characteristic of theinvention are used the quality of motor fuel (and sometimes its yield)is improved over that obtained with diierent flow methods at otherwiseidentical quantities and temperatures Unexpectedly, these advantages areobtained without sacrice of additional conversion of charge to cokydeposit which :must be removed' from the catalyst during regen'-eration.

obtained with other methods yielding equivalent quantities and qualityof motor fuel, permitting increased reactor or conversion capacityy with-respect to concomitant burning or regenerator capacity. l

Certain of the above advantages and others accruing to practice of theinvention are reflected y y'inv the following specific and typicalexamples:

Example I 'Cracking Catalystsby J. Alexander andHjG.

Shimp, ypage Rr53'7, National Petroleum News,

'August 2, 1944. Run A was made in accordance "with the process of theinvention, the vaporized 4charge owing through the reactor forsubstantially the entire depth of the'catalyst bed therein concurrentlywith the catalyst flow. In run B,

`ei'lected in accordance with'prior procedure, the

conditions of space velocity, "oil and catalyst feed temperature andrelative rates of feed, reactor pressure and other general conditionswere substantially identical with those Yemployed for run A, exceptingthe direction of flow of the charge through the reactor. In run B thehot vaporized charge was admitted adjacent the bottom of the reactorkand products were withdrawn adjacent the top of the moving bed ofcatalyst.

Y The comparative conditions of runs A and B and the yields of productswith inspections of motor gasoline obtained are summarizedv in thefollowing table:

Run Run A B OPE RATIN G CONDITIONS Space Velocity, Volumes originalliquid charge per hour und per volume of catalyst in reactor 0. Sl 0. 78Ratio of Catalyst to Oil Charge, volume/volume 2.05 2. 03 Charge FeedTemperature, E. 900 900 Catalyst Feed Temperature, E. 1000 1000 SteamFeed with Charge, Per cent Wt. of charge. 9. 7 -l0. 2 Reactor Pressure,Lbs/sq. in. gauge Y 10 10 'YIELDS BASED ON CHARGE- l() Ll). R. V. P.Motor Gasoline, 370 FL' 90%, Per

CentVol :1. 37.9 36.5 C4 Free Motor Gasoline, 370 90%, `Per Cent Vol35.8 34. 2 Catalytic Gas Oil (420 F. to 750c F.), Per'Ccnt Vol 49. 754.5 Conversion, Per Cent Vol. (100% Less Cracked Fuel). 50. 3 45. 5Total 04's, Per `Cent Vol. 12.4 10.3 Total Recovered Liquid (Ors andbeaver) Per Cent Vol 97. 9 99. 0 Dry Gas (03's and lighter), Per Cent Y6. 2 5. 0 Coke, Por Cent Wt.:

Octanes of Motor Gasoline (i0 Lb. TLV. P.) 2. 9 By Method F-Z (CRCDesignation F Handbook. 1946 Edition) unleaded. 78. 7 By Method F-l (CRCDesignation F1545, CR

Handbook, 1946 Edition) unleade(= 88. 5 +1 cc. TEL/gal 92.3 +3 cc.TEL/gal. 94. 4

Under the conditions of these runs heat capacity of the oil feedwasapproximately 1.8 times that of the catalyst.

Itis to be noted'froin this examplev that the process of the inventionyields'substantially improved octane motor fuel in higher yield at iden--[tical oil feed and catalyst feed temperatures. In Y "tially belowoilfeed temperature.

fact,- the gain` of gasoline yield in run A over run B is greater thanthe loss of liquid product.

Example 2 A third run (run C) Aon the same, charge and catalyst as usedin runs A. and B was performed, in accordance with .the process'of theinvention, under conditions to produce motor fuel of qualityequivalentto that obtained from run B. Essentially space velocities andcatalyst-to-oilratios were the same as used in runs A and B as Well vasquantity of steam fed with the charge and reactor pressure. Theoperating conditions and results of this run are as follows:

Operating Conditions Total Liquid Rec Dry Gas, Cas and lighte Coke yOctanes 0f Gasoline (l0 Lb. R. V. P., 370 F. 90%):

1"-2 Method, unleaded F-l Method, unleaded It is evidentfrom this runthat practice of the `invention achieves, without sacrifice of qualityof gasoline, yields of gasoline and liquid products at least equal toand even somewhat greater than obtained by countercurrent flow of thecatalyst bedzan'd oil charge vapors at the same relative rates of feedof these materials. This result is obtained at lower temperatures ofsuch feeds land with concomitant production of smaller quantities ofcoky deposit than indicated for run B. In operating a commercial scalecracking unit of a capacity commonly used (10,000 barrels of charge perday) the quantity of coke deposit urider the conditions of run C wouldapproximate about 520 pounds of coke per hour less than obtained at theconditions of run B, permitting equivalent reduction in rate of burningin the kiln. v Y

As mentioned above, in practice of the invention the catalyst and oilvapors decrease gradually in temperature while flowing through thereactor. Since, by preference, the catalyst as admitted thereto is athigher temperature than the hot oil vapors, the catalyst imparts heat'to the oil, heating it rapidly to the desired initial crackingtemperature. After this initial preheating of the oil, a gradualtemperature decline occurs until the catalyst and oil vaporscontainingfgasoline are separated adjacent the bottom ofthe reactor. Inview of the fact that the heat capacity of the oil vapors is 'greaterthan that of the catalyst the average temperature level attained by thecatalyst and oil approaches and even .approximates that of the oil feed,avoiding excessive localized oil temperatures and overcrackingof thecharge to coky deposit.

On the other hand, when, according to prior practice, the oil vapors areadmitted adjacent the bottom of the reactor to ow countercurrently tothe'catalyst, the latter declines gradually'in temperature while flowingthrough the upper and central portions of` the reactor to levelssubstan- The catalyst then becomes reheated toward oil feed tempera#ture in the bottom portion of the same. As a re- .lof-the invention withidentical catalystand oil feed temperatures: Thus, in run A of Examplel,

4the average cracking temperatiue wassomewhat yabove that of the oilcharge, about 905- F.

In run B the' average temperature was Asubstantially ,below that level,or about 850?. .In run C also average temperature of about 850 F. wasobtained, despite the relatively low temperatures of oil and catalystfeed.

In order to obtain, by prior methods in which charge oil .vapors passcountercurrently to ther compact bed of catalyst, the high quality ofmotor lgasoline realized by practice of the invention at ,relativelyhigh temperatures and as exemplied 'by run A, it has been necessary toresort to .ratios of catalyst to' oil feeds such that the-heat c'apacityof the catalyst exceeds that of themoil. For C Xample, to achieve withthe countercurrent flow In addition, with the prior practice, desiredincrease in severity of cracking tocbtain the high quality of productcharacteristic of'preferred aplplication of the invention waspractically impos- -sible of attainment by adjustment of the temperatureof the oil charge. The charge temperatures necessary were well Withinthe rangeat which -thermal cracking depreciates quality of gasoline. 'Onthe other hand, in practice of the invention, -there is, unexpectedly,at low ratios of catalyst to oil feeds `and at desirably low oil feedtemperatures, more direct and vefficient utilization of the `total heatcontent of the catalyst and oil feeds.

It is therefore evident that the-process of the inl'vention provides forhighly flexible operationto meet requirements as they may changeforqualy i ity and yield of `gasoline and for yield of other products,including catalytic gas oil.

Although the above examples, for purposes of comparison, deal with runseffected at but one space velocity, quantity of steam feed and `presv.

sure, it is to be understood that the invention contemplates otherspecic levels of these conditions that it is or may become desirable orpractical to luse. For example, space velocities may lie Within oroutside the range of about 0.4 to 3.0. With some charging stocks, forexample, relatively heavy gas oils, larger or smaller quantities ofsteam feed? may be used. With relatively light charging stocks whichr'nayv be considered to in- "clude East Texas gas oil of the characterused in the runs of the specific examples, it'is sometimes desirable touse smaller quantities of steam feed or none at all.

In connection with the above examples, it

should be pointed out that'the anti-knock ratings' obtained by run A arehigh considering the degree of conversion of the charge employed togasoline, dry gas and coke, respectively, and considering the nature ofthat charge and the catalyst. Other charging stocks, for example, light`and heavy gas oils of naphthenic base crudes tend to yield even higheroctane ratings. Also certain "cracking catalysts among the general classof crackingcatalysts, all of which are suitable for lpractice of theinvention, tend to produce higher octant rating motor fuels than do claycatalysts vof .the type employed in the runs of the specific examples.Catalysts tending to produce the higher octanes include composites ofsynthetically prepared silica and alumina derived from precipitated gelsand preferably substanially free of any alkali metal compounds that mayhave been used in their preparation.

The invention is susceptible of variations and modications of theforegoing description and explanation thereof that are included withinthe .scope of the appended claims.

I claim as my invention:

1. In a hydrocarbon cracking system in which granular hydrocarboncracking catalyst continuously circulates through a systemy comprising ahydrocarbon cracking zone in which a down- Wardly moving compactnon-turbulent bed of said catalyst contacts hydrocarbon material boilinghigher than gasoline under cracking conditions and thereby concomitantlyaccumulates a coky ldeposit and a regeneration zone in which cokedcatalyst from the-cracking Zone contacts oxygen containing gas undercombustion lcondi-- tions so as to remove a predetermined amount of Y,coky deposit and thereby reactivate said coked catalyst;.the method ofmaintaining constant the amount of coke deposited on said catalyst inthecracking zone and simultaneously troducing said stream of catalyst tolthe cracking zone at a substantially constant temperature considerablyabove the average temperature of the bed of catalyst therein,introducing said stream of hydrocarbon material to the top of thecracking zone at a temperature below the temperature of the stream ofcatalyst introduced to the cracking zone, passing said hydrocarbonmaterial in vapor state downwardly through said bed of catalyst,reactivating coked catalyst under constant combustion conditions in saidregeneration Zone, and adjusting the temperature of introduction of saidstream of hydrocarbons tol the cracking zone so as to maintain aconstant severity of cracking of said hydrocarbon material in saidcracking zone. l 2. In a hydrocarbon cracking system in whic granularhydrocarbon cracking catalyst continuously circulates through a-systemcomprising a hydrocarbon cracking zone in which a downwardly movingcompact non-turbulent bed of said catalyst contactsy hydrocarbonmaterial boiling higher than gasoline under cracking conditions andthereby concomitantly accumulates a coky deposit and a regenerationzonein which coked catalyst from the cracking zone contacts oxygencontaining gas under combustion conditions so as to remove apredetermined amount of coky deposit and thereby reactivate said cokedcatalyst; the method of maintaining constant the amount of cokedeposited on said catalyst in the cracking zone and simultaneouslyVobtaining relatively high yields of high occomprises establishingrelative rates of ow of streams of catalyst and of hydrocarbon materialthrough the cracking zone such that the heat capacity of the stream ofhydrocarbon material introduced to the cracking zone is greater thanthat of the stream of catalyst introduced to the cracking zone but lessthan one and a half times asgreat, introducing said stream of catalystto the cracking zone at a substantially constant temperatureconsiderably above the average temperature of the bed of catalysttherein and in the range of 850 F. to 1050 F., introducing said streamof hydrocarbon material to the top of the cracking zone at a temperatureabove about 850 F. and below the temperature of the stream of catalystintroduced to the cracking Zone, passing said hydrocarbon material invapor state downwardly through said bed of catalyst, reactivating cokedcatalyst under constant combustion conditions in said regeneration zone,and adjusting the temperature of introduction of said stream ofhydrocarbons to the cracking zone so as to maintain a constant Thefollowing references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,379,408 Arveson July 3, 19452,403,375 Kassel July 2, 1946 2,418,679 Utterback Apr. 8, 1947 2,440,822Hachmuth May 4, 1948 2,441,170 Rose et a1. May 11, 1948 OTHER REFERENCESCommercial T. C. C. Operationson Partially Vaporized Charge Stocks, Nollet al., Houdry .30 Pioneer, Vol. 2, No. l, Oct. 1946.

Recent Developments in Thermofor Catalytic Cracking Process, Simpson etal., Nat. Pet. News, Dec. 1, 1943.

1. IN A HYDROCARBON CRACKING SYSTEM IN WHICH GRANULAR HYDROCARBONCRACKING CATALYST CONTINUOUSLY CIRCULATES THROUGH A SYSTEM COMPRISING AHYDROCARBON CRACKING ZONE IN WHICH A DOWNWARDLY MOVING COMPACTNON-TURBULENT BED OF SAID CATALYST CONTACTS HYDROCARBON MATERIAL BOILINGHIGHER THAN GASOLINE UNDER CRACKING CONDITIONS AND THEREBY CONCOMITANTLYACCUMULATES A COKY DEPOSIT AND A REGENERATION ZONE IN WHICH COKEDCATALYST FROM THE CRACKING ZONE CONTACTS OXYGEN CONTAINING GAS UNDERCOMBUSTION CONDITIONS SO AS TO REMOVE A PREDETERMINED AMOUNT OF COKYDEPOSIT AND THEREBY REACTIVATE SAID COKED CATALYST; TH METHOD OFMAINTAINING CONSTANT THE AMOUNT OF COKE DEPOSITED ON SAID CATALYST INTHE CRACKING ZONE AND SIMUTANEOUSLY OBTAINING RELATIVELY HIGH YIELDS OFHIGH OCTANE GASOLINE FROM SAID HYDROCARBON MATERIAL AT RELATIVELY LOWRATES OF CATALYST FLOW, WHICH METHOD COMPRISES ESTABLISHING RELATIVERATES OF FLOW OF STREAMS OF CATALYST AND OF HYDROCARBON MATERIAL THROUGHTHE CRACKING ZONE SUCH THAT THE HEAT CAPAICTY OF THE STREAM OFHYDROCARBON MATERIAL INTRODUCED TO THE CRACKING ZONE IS GREATER THANTHAT OF THE STREAM OF CATALYST INTRODUCED TO THE CRACKING ZONE BUT LESSTHAN TWICE AS GREAT, INTRODUCING SAID STREAM OF CATALYST TO THE CRACKINGZONE AT A SUBSTANTIALLY CONSTANT TEMPERATURE CONSIDERABLY ABOVE THEAVERAGE TEMPERATURE OF THE BED OF CATALYST THEREIN, INTRODUCING SAID